The present invention relates to a blocked isocyanate group-containing resin composition, and more particularly, it relates to a blocked isocyanate group-containing resin composition excellent in curability at low temperature and compatibility with base resins for paint and useful as a curing agent component, and a thermosetting composition containing the same.
Recently, in view of the environmental preservation, it has been required to reduce the energy consumption at a paint baking step. On the other hand, the application of a baking paint to materials having a low thermal resistance has been desired owing to diversified substrates to be applied. For these demands, a paint wherein a resin having isocyanate groups blocked with an active methylene compound such as an acetoacetate ester or a malonate diester is used as a curing agent is promising because it is cured at a relatively low temperature. Various resins having isocyanate groups blocked with an active methylene compound are disclosed in, for example, Japanese Laid-Open Patent Publication Nos. 60-149572/1985, 57-121065/1982, 8-319332/1996, 10-231347/1998, 10-231348/1998.
However, the above resins having isocyanate groups blocked with an active methylene compound have defects that they sometimes crystallize at a low temperature or they tend to become inhomogeneous or clouded through phase separation into an islands-sea structure depending on the base resin component used owing to their low compatibility with common resins for paint. Therefore, they involve a problem that the kind of resins usable is limited and thus freedom at paint design is restricted. As a measure against the problem, Japanese Laid-Open Patent Publication No. 6-16769/1994 discloses a method of reacting, with a monohydric alcohol, isocyanate groups other than the isocyanate groups blocked with an active methylene compound. The method described in the publication improves the above defects to some extent but the compatibility with resins for paint is still insufficient.
On the other hand, in view of advanced environmental preservation, the use of water-based paints has been required. However, when the resins having isocyanate groups blocked with an active methylene compound are used as curing agents for water-based paints, the resulting water-based paints have poor viscosity-stability at storage and thus are accompanied by a problem that the paint viscosity decreases largely with the passage of time and the workability at painting remarkably lowers.
As a result of an extensive studies for solving the above problem, the present inventors have found that a resin obtainable by modifying a resin having blocked isocyanate groups of a specific structure with a specific alcohol and having a solubility parameter value lower than that of the resin before the modification is excellent in compatibility with various base resin components for paint and is useful as a curing agent, and therefore, they have accomplished the present invention.
The present invention relates a blocked isocyanate group-containing resin composition, comprising a resin (C) obtainable by modifying a resin (A) having, in one molecule, two or more blocked isocyanate groups represented by the following formula (I) or (II): 
wherein R1, R2, R3, and R4, which are the same or different, each represents a substituent having 1 to 10 carbon atoms, with a monohydric alcohol (B) represented by the following formula (III):
R5OHxe2x80x83xe2x80x83(III) 
wherein R5 represents a substituent having 3 to 8 carbon atoms, whereby at least one of R1, R2, and R3 in the blocked isocyanate group in the resin (A) is replaced by R5. The resin (C) exhibits a lowered solubility parameter as compared with the resin (A).
The resin (A) may be obtained by reacting the isocyanate groups in a polyisocyanate compound (a) having at least two isocyanate groups in one molecule with an active methylene compound (b). Part of the isocyanate groups in the polyisocyanate compound (a) may be reacted with a monohydric alcohol. The resin (A) may be a resin obtainable by homopolymerizing a vinyl monomer containing a blocked isocyanate group represented by the formula (I) or (II), or copolymerizing the monomer with other vinyl monomer.
The R5 in the monohydric alcohol (B) may be a substituent having 5 to 18 carbon atoms containing no hetero atom. The monohydric alcohol (B) may be one or more selected from mono(or oligo)propylene glycol monoalkyl ethers having 4 to 10 carbon atoms, mono(or oligo)ethylene glycol monoalkyl ethers having 4 to 10 carbon atoms, and aliphatic alcohols having 4 to 10 carbon atoms. The R5 in the monohydric alcohol (B) may be a group having more number of carbon atoms than the number of carbon atoms of least one of R1, R2, and R3 in the resin (A).
The resin (C) may be obtainable by removing part or all of the alcohol derived from at least one selected from R1, R2, and R3 in the blocked isocyanate groups in the resin (A). In this case, part or all of the alcohol derived from at least one selected from R1, R2, and R3 in the blocked isocyanate groups in the resin (A) may be removed by heating and vacuuming operation.
In the present invention, the resin (A) has two or more blocked isocyanate groups represented by the above formula (I) or (II) in one molecule, and is usually obtained by reacting the isocyanate groups in a polyisocyanate compound (a) having at least two isocyanate groups in one molecule with an active methylene compound (b). In the above formula (I) or (II), R1, R2, R3, and R4, which are the same or different, each represents a substituent having 1 to 10 carbon atoms, and the substituent may contains a hetero atom and is preferably a substituent having 1 to 8 carbon atoms.
Examples of the above polyisocyanate compound (a) include diisocyanates having 4 to 25 carbon atoms such as diphenylmethane-4,4xe2x80x2-diisocyanate (MDI), 1,5-naphthalene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate, 1,4-tetramethylene diisocyanate, 2-methyl-1,5-diisocyanatopentane (MPDI), 1,6-diisocyanatohexane (HDI), 2,2,4-trimethyl-1,6-hexamethylene diisocyanate (TMDI), lysine diisocyanate, 1-isocyanato-3,5,5-trimethyl-3-(isocyanatomethyl)cyclohexane (IPDI), dicyclohexylmethane-4,4xe2x80x2-diisocyanate (HMDI), m-tetramethylxylylene diisocyanate (TMXDI), diisocyanatonorbornane, and di(isocyanatomethyl)norbornane, triisocyanates having 6 to 30 carbon atoms such as 2-(isosyanatoethyl)-2,6-diisocyanatocaproate (LTI), adducts of these di- or triisocyanates with a polyhydric hydroxyl group-containing compound, a monohydric alcohol, or water; polyisocyanates containing a urethane structure, a biuret structure, an isocyanurate structure, an allophanate structure, or a urethodione structure, and having a number-average molecular weight of 300 to 20000 and an average number of isocyanate groups in one molecule of 2 to 100; polyisocyanates obtainable by homopolymerizing isocyanate group-containing vinyl monomers such as (meth)acryloyl isocyanate, 2-isocyanatoethyl (meth)acrylate, m-isopropenyl-xcex1,xcex1xe2x80x2-dimethylbenzyl isocyanate, and 1:1 adducts of hydroxyl group-containing vinyl monomers with the above diisocyanates, or copolymerizing the isocyanate group-containing vinyl monomers with other vinyl monomers such as (meth)acrylate esters and vinyl aromatic compounds, and having a number-average molecular weight of 1000 to 20000, and an average number of isocyanate groups in one molecule of 2 to 100; and the like. These may be used singly or as a combination of two or more of them. Moreover, a polyisocyanate derived from one of these various polyisocyanates, and one or more selected from polyhydric hydroxyl group-containing compound, water and monohydric alcohols having a molecular weight of 32 to 400, and having a number-average molecular weight of 300 to 20000 and an average number of isocyanate groups in one molecule of 2 to 100 can be also used as the polyisocyanate compound (a).
Among these polyisocyanates, particularly preferred are isocyanurate type polyisocyanates of diisocyanates or isocyanurate type polyisocyanates of adducts of diisocyanates with a polyhydric hydroxyl group-containing compound, a monohydric alcohol, or water. The modification with a polyhydric hydroxyl group-containing compound, a monohydric alcohol, or water is a urethanization reaction with an isocyanate group, and may be carried out before or after the isocyanuration of the polyisocyanates. In the isocyanuration, a catalyst may be used. The catalyst is suitably a basic compound such as a metal hydroxide, a metal alkoxide, a metal carboxylate, a metal acetylacetonate, hydroxide of an onium salt, an onium carboxylate, a metal salt of an active methylene compound, or an onium salt of an active methylene compound or a Lewis acid such as an organotin compound. The onium salt is preferably an ammonium salt, a phosphonium salt, or a sulfonium salt. Usually, the amount of the catalyst is suitably in the rage of 10 to 10000 ppm, particularly 20 to 5000 ppm. The reaction may be carried out at 0xc2x0 C. to 150xc2x0 C. When the reaction has proceeded as aimed, the reaction may be terminated by neutralizing the basic compound of the catalyst. Unreacted isocyanates may be optionally removed after the completion of the isocyanuration.
The above polyhydric hydroxyl group-containing compound is a polyol having a number-average molecular weight of 60 to 10000 and two or more hydroxyl groups in one molecule, and examples thereof include compounds having two or more hydroxyl groups in one molecule, such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, butanediol, polytetramethylene glycol, methylpropanediol, pentanediol, methylpentanediol, hexanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, hydroxypivalic acid-neopentyl glycol ester, dimethylolpropanoic acid, dimethylolbutanoic acid, trimethylolethane, trimethylolpropane, trimethylolbutane, glycerol, and pentaerythritol; at least one ring-opening adduct of one of these compounds and one compound selected from ethylene oxide, propylene oxide, tetrahydrofuran, a lactone and a cyclic carbonate; reaction products of compounds having both of an amino group and hydroxyl group in one molecule with an epoxy group-containing compound, reaction products of compounds having both of an amino group and hydroxyl group in one molecule with a polyisocyanate, polyesters containing hydroxyl groups, polyurethanes having hydroxyl groups, vinyl copolymers containing hydroxyl groups, epoxy resins, and the like.
The resin (A) is usually a compound obtainable by reacting the isocyanate groups in the above polyisocyanate compound (a) with an active methylene compound (b), but the resin can be also obtained by homopolymerizing a blocked isocyanate group-containing vinyl monomer represented by the above formula (I) or (II) or copolymerizing the monomer with other vinyl monomer beforehand. The blocked isocyanate group-containing vinyl monomer is obtainable by blocking the above isocyanate group-containing vinyl monomer with an active methylene compound or by blocking the isocyanate group present at the one end of one of the above diisocyanates with an active methylene compound and then reacting the remaining isocyanate groups with a hydroxyl group-containing vinyl monomer. Particular, in view of the yield, preferred are compounds obtainable by the latter method.
Examples of the active methylene compound (b) blocking the isocyanate groups in the above polyisocyanate compound (a) include malonate esters such as dimethyl malonate, diethyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, di-sec-butyl malonate, di-t-butyl malonate, di(2-ethylhexyl) malonate, methyl isopropyl malonate, ethyl isopropyl malonate, methyl n-butyl malonate, ethyl n-butyl malonate, methyl isobutyl malonate, ethyl isobutyl malonate, methyl sec-butyl malonate, and ethyl sec-butyl malonate; acetoacetates such as methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, isobutyl acetoacetate, sec-butyl acetoacetate, and t-butyl acetoacetate; xcex2-diketones such as acetylacetone. These may be used singly or as a combination of two or more of them. Among them, particularly preferred is diethyl malonate or ethyl acetoacetate.
At the blocking reaction of the isocyanate group with the above active methylene compound (b), a reaction catalyst may be used, if necessary. The reaction catalyst is suitably a basic compound such as a metal hydroxide, a metal alkoxide, a metal carboxylate, a metal acetylacetonate, a hydroxide of onium salt, an onium carboxylate, a metal salt of active methylene compound, an onium salt of active methylene compound, an aminosilane, an amine, a phosphine, or the like. Among them, the onium salt is preferably an ammonium salt, a phosphonium salt, or a sulfonium salt. Usually, the amount of the catalyst is suitably in the range of 10 to 10000 ppm, particularly 20 to 5000 ppm relative to the total amount of the isocyanate compound and the active methylene compound. The above reaction may be carried out at 0xc2x0 C. to 150xc2x0 C., and a solvent may be used. In this case, the solvent is preferably a non-protic solvent, and particularly preferred is an ester, an ether, an N-alkylamide, a ketone, or the like. When the reaction has proceeded as aimed, the reaction may be terminated by adding an acid to neutralize the basic compound of the catalyst.
The amount of the active methylene compound (b) to be used is not particularly limited but is preferably from 0.1 to 3 equivalents, more preferably 0.2 to 2 equivalents relative to 1 equivalent of the isocyanate group in the polyisocyanate compound (a). Unreacted active methylene compound can be removed after the blocking reaction.
Moreover, other than the above active methylene compound (b), a blocking agent such as an alcohol, a phenol, an oxime, an amine, an acid amide, an imidazole, a pyridine, or a mercaptan may be used in combination within the range at which curability at low temperature is not inhibited.
Moreover, part of the isocyanate groups in the above polyisocyanate compound (a) may be reacted with at least one selected from the above polyhydric hydroxyl group-containing compound, water and the monohydric alcohol, and in particular, preferably reacted with monohydric alcohol in view of the compatibility with a base resin component. The order of the reaction with the active methylene compound (b) may be the order that necessary amount of the isocyanate groups are blocked with the active methylene compound (b) and then the remaining isocyanate groups are reacted with a monohydric alcohol, or the reverse order, or the active methylene compound (b) and a monohydric alcohol may be reacted with the isocyanate groups all at once. Examples of the monohydric alcohol include propanol, butanol, hexanol, heptanol, 2-ethylhexanol, octanol, nonanol, decanol, tridecanol, stearyl alcohol, and isomers thereof, mono (oligo or poly)ethylene glycol monoalkyl ethers, mono(oligo or poly)propylene glycol monoalkyl ethers, and the like. Since too much use of the monohydric alcohol sometimes causes decrease of curability, the amount of the monohydric alcohol to be used is suitably 0.6 equivalent or less, preferably 0.4 equivalent or less relative to 1 equivalent of the isocyanate group in the polyisocyanate compound (a).
The resin (A) having two or more blocked isocyanate groups represented by the following formula (I) or (II) in one molecule, obtained as above, has suitably a number-average molecular weight of 500 to 20000, preferably 800 to 18000. When the molecular weight is less than 500, the curability of the resulting coated film is lowered. On the other hand, when the molecular weight exceeds 20000, the appearance of the coated film is lowered. Thus, both cases are not preferred. Moreover, the resin (A) has desirably a solubility parameter value ranging from 8.2 to 11.5, preferably from 8.3 to 11.3. The solubility parameter value (hereinafter, sometimes abbreviated as xe2x80x9cSP valuexe2x80x9d) is a measure of solubility. When the value is too large or too small, the compatibility with common base resins for paint frequently decreases. In the present invention, the value is a numerical value obtainable by actual measurement in accordance with turbidimetric titration method as shown in the following.
In the turbidimetric titration method, a resin is dissolved in a good solvent, and a poor solvent is added dropwise to measure the amount of the poor solvent required for occurrence of clouding. This measurement is carried out separately using two kinds of poor solvent, i.e., a poor solvent having a small SP value (n-hexane or the like) and a poor solvent having a large SP value (deionized water or the like). Specifically, 0.5 g of a resin to be measured is weighed in a 100 ml beaker, and is dissolved in 10 ml of acetone. Two of this solution are prepared. Next, a poor solvent, n-hexane is added dropwise to one of them by means of a buret and the amount of n-hexane required for occurrence of clouding was measured (the amount is referred to as H (ml)). For another solution, a similar experiment is carried out using deionized water as a poor solvent and the amount of deionized water required for occurrence of clouding is measured (the amount is referred to as W (ml)). The titration is carried out in a constant-temperature room at 20xc2x0 C. The SP value is determined by substituting H and W into the following equation.
xe2x80x83SP value=((9.75xc3x97(1xe2x88x92xcex1)+7.24xc3x97xcex1)xc3x97(xcex1)+(9.75xc3x97(1xe2x88x92xcex2)+23.43xc3x97xcex2)xc3x97(xcex2))/((xcex1)+(xcex2))
provided that xcex1=H/(H+10), and xcex2=W/(W+10).
By the way, the values 9.75, 7.24, and 23.43 derive from the SP values of acetone, n-hexane, and deionized water, respectively.
In the present invention, the above resin (A) is modified with a monohydric alcohol (B) represented by the above formula (III) to obtain the resin (C) wherein at least one of R1, R2, and R3 in the blocked isocyanate groups in the resin (A) is replaced by R5. The resin (C) has a lowered SP value as compared with the above resin (A). The above monohydric alcohol (B) is a compound represented by the above formula (III) wherein R5 represents a substituent having 3 to 18 carbon atoms, and the substituent may or may not contain a hetero atom. In the case that a hetero atom is contained, a substituent having 5 to 18 carbon atoms is suitable and in particular, a substituent having 6 to 18 carbon atoms is preferred. In the case of a substituent having 1 or 2 carbon atoms, the SP value of the resin (C) is not lowered. On the other hand, in the case of a substituent having more than 18 carbon atoms, the dissolving power of the resin (A) sometimes decreases. Thus, both cases are not preferred.
Examples of the monohydric alcohol (B) include aliphatic alcohols such as propanol, butanol, pentanol, hexanol, 2-ethylhexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, and isomeric alcohols thereof; mono(or oligo)ethylene glycol monoalkyl ethers such as ethylene glycol monoalkyl ethers, diethylene glycol monoalkyl ethers, triethylene glycol monoalkyl ethers, and tetraethylene glycol monoalkyl ethers; mono(or oligo)propylene glycol monoalkyl ethers such as propylene glycol monoalkyl ethers, dipropylene glycol monoalkyl ethers, tripropylene glycol monoalkyl ethers, and tetrapropylene glycol monoalkyl ethers; mono(or oligo)ethylene glycol monoesters such as ethylene glycol monoesters, diethylene glycol monoesters, triethylene glycol monoesters, and tetraethylene glycol monoesters; mono(or oligo)propylene glycol monoesters such as propylene glycol monoesters, dipropylene glycol monoesters, tripropylene glycol monoesters, and tetrapropylene glycol monoesters; and the like. These compounds may be used singly or as a combination of two or more of them. The monohydric alcohol (B) is suitably selected depending on R1, R2, and R3 in the resin (A).
Among the exemplified compounds, in view of the storage stability in water-based paints, preferred is a monohydric alcohol wherein R5 is a substituent containing no hetero atom and having 5 to 18, preferably 6 to 15 carbon atoms, and particularly preferred is an aliphatic alcohol having 6 to 15 carbon atoms also from the viewpoint of dissolving power. An alcohol having less than 4 carbon atoms is not preferred since the viscosity of the resulting water-based paint sometimes decreases largely at the storage.
On the other hand, among the exemplified compounds, in the case of the use for organic solvent-based paints, preferred are particularly mono(or oligo)propylene glycol monoalkyl ethers having 4 to 10 carbon atoms such as propylene glycol monomethyl ether and propylene glycol monopropyl ether; mono(or oligo)ethylene glycol monoalkyl ethers having 4 to 10 carbon atoms such as ethylene glycol monobutyl ether, and aliphatic alcohols having 4 to 10 carbon atoms in view of dissolving power.
The number of carbon atoms of R5 in the above formula (III) may be optionally selected depending on the number of carbon atoms of R1, R2, and R3 in the blocked isocyanate groups in the resin (A). For particularly efficiently lowering the SP value, the number of carbon atoms of R5 is preferably more than the number of carbon atoms of any of R1, R2, and R3. When the number of carbon atoms of R5 is less than the number of carbon atoms of any of R1, R2, and R3, the SP value is not lowered in many cases even after the modification, and thus, the case is not preferred.
In the present invention, the procedure for modifying the resin (A) with the monohydric alcohol (B) is not particularly limited as far as the procedure is capable of replacing at least one of R1, R2, and R3 in the blocked isocyanate group in the resin (A) by R5, but it is desirable to use the procedure of obtaining the resin (C) by removing part or all of the alcohol derived from at least one of R1, R2, and R3 in the resin (A) from the system into outside through distillation or the like by heating or vacuuming. With regard to the conditions, it is suitable to remove part or all of the above alcohol at a temperature of 20 to 180xc2x0 C., preferably 40 to 130xc2x0 C. over a period of 5 minutes to over ten hours, preferably 10 minutes to 10 hours and, if necessary, under reduced pressure. Too low temperature is not preferable since the SP value of the resulting resin (C) is hardly lowered possibly owing to slow exchange of the alkoxy group. Also, too high temperature causes coloration and thus, is not preferable. Moreover, in order to control the molecular weight of the resin (C), the above removing operation may be carried out after the addition of the above polyhydric hydroxyl group-containing compound to the resin (A) in addition to the monohydric alcohol (B).
The amount of the monohydric alcohol (B) to be used for the modification is from 5 to 500 parts by weight, preferably 10 to 200 parts by weight relative to 100 parts by weight of solid content of the resin (A). When the amount is less than 5 parts by weight, the effect of the modification becomes small and thus the SP value of the resulting resin (C) is hardly lowered. On the other hand, the use of the alcohol in an amount exceeding 500 parts by weight is economically disadvantageous in view of the cost. Thus, both cases are not preferred.
The resin (C) obtainable as above is a resin having two or more blocked isocyanate groups in one molecule and has an SP value lower than that of the resin (A). The SP value is desirably in the range of 8.0 to 11.0, preferably 8.1 to 10.8. Moreover, the number-average molecular weight of the resin (C) is desirably in the range of 600 to 30000, preferably 900 to 25000. When the molecular weight is less than 600, the curability of the resulting coated film is lowered, and when the molecular weight exceeds 30000, the appearance of the coated film is lowered. Thus, both cases are not preferred. The resin (C) thus obtained has a largely improved compatibility with the common resins for paint and also, a largely improved storage stability in the case of the use for water-based paints.
The present invention also provides a thermosetting composition comprising the resin (C) obtained as above and a polyol (D). The thermosetting composition is a composition usually comprising the resin (C) as a curing agent component and the polyol (D) as a base resin component.
As the above polyol (D), those hitherto known as base resins for paint are applicable without particular limitation. Usually, vinyl resins, polyester resins, polyurethane resins, polyurethane polyester resins, fluorine resins, silicon resins, and the like having a number-average molecular weight of 1000 to 80000, preferably 1200 to 60000 and a hydroxyl value of 5 to 220 mg KOH/g (solid content), preferably 10 to 200 mg KOH/g can be used. These compounds may be used singly or as a combination of two or more of them. When the number-average molecular weight of the polyol (D) is smaller than 1000, the curability of the resulting coated film is lowered, and when the molecular weight exceeds 80000, the appearance of the coated film is lowered. Thus, both cases are not preferred. Moreover, the hydroxyl value is smaller than 5 mg KOH/g, the curability of the resulting coated film is lowered, and when the value exceeds 200 mg KOH/g, the water resistance of the coated film is decreased. Thus, both cases are not preferred.
The above polyol (D) can be used as an organic solvent soluble form or a dispersed form, and may contain, if necessary, a croslinking functional group such as carboxyl group, carbonyl group, silanol group, or epoxy group, and a water-soluble functional group such as sulfonic acid group, phosphoric acid group, a metal carboxylate group, a metal sulfonate group, a metal phosphate group, an onium carboxylate group, an onium sulfonate group, an onium phosphonate group, poly(ethylene oxide) group, poly(propylene oxide) group, or poly(ethylene oxide/propylene oxide) group. As such an onium, preferred is ammonium, phosphonium, or sulfonium. In the case that the polyol (D) has the water soluble functional group, it may be used as such or neutralized with a neutralizing agent or the like. The content of the water-soluble functional group is not particularly limited but in view of water resistance, the content is preferably 2.0 mmol/g (solid content) or less in the polyol.
Among the above examples of the polyol (D), as the vinyl resins, the compounds known per se can be used and examples thereof include acrylic resins and vinyl resins obtainable by copolymerizing a hydroxyl group-containing monomer with other polymerizable monomer. These resins can be obtained by solution polymerization, emulsion polymerization, or suspension polymerization. Examples of the hydroxyl group-containing monomer include hydroxyalkyl esters of (meth)acrylic acid such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and ring-opening adducts of these compound to one compound selected from ethylene oxide, propylene oxide, tetrahydrofuran, lactones, and cyclic carbonates. Examples of other polymerizable monomer include alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, and itaconic acid; acrylamide derivatives such as (meth)acrylamide, N-methylolacrylamide, and diacetone acrylamide; glycidyl (meth)acrylate, vinyl acetate, vinyl propionate, styrene, xcex1-methylstyrene, vinyltoluene, and the like. These compounds may be used singly or as a combination of two or more of them.
Among the above examples of the polyol (D), as the polyester resins, the compounds known per se can be used and examples thereof include polyester resins obtainable by esterification of polyhydric alcohols with polybasic acids. Examples of usable polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, 2,2-dimethylpropanediol (neopentyl glycol), 2-butyl-2-ethyl-1,3-propanediol, glycerol, trimethylolpropane, trimethylolethane, pentaerythritol, and the like. Examples of usable polybasic acid include phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, succinic anhydride, adipic acid, sebacic acid, trimellitic anhydride, pyromellitic anhydride, and the like. Furthermore, if necessary, monobasic acids such as benzoic acid and t-butylbenzoic acid, and caster oil, tung oil, safflower oil, soybean oil, linseed oil, tall oil, coconut oil, oil components derived from these fatty acids, as well as epoxy compounds such as glycidyl ester of neodecanoic acid can be used.
In the thermosetting composition of the invention, the using ratio of the resin (C) and the polyol (D) is preferably in the range of 1:0.5 to 1:20 based on the solid content of the both components. The ratio lower or higher than the range is not desirable since the curability is lowered in many cases.
Into the thermosetting composition of the invention, other than the above resin (C), a curing agent capable of reacting with the crosslinking functional group in the polyol (D), for example, a melamine resin, a urea resin, an epoxy group-containing compound or resin, a carboxyl group-containing compound or resin, an acid anhydride, an alkoxysilane group-containing compound or resin, a hydrazide compound may be incorporated, if necessary.
The thermosetting composition of the invention may be any form such as solvent-type or water-based. In any case, the composition can be cured by maintaining it at 60 to 160xc2x0 C. for several minutes to several hours. At that time, the curing may be accelerated by adding a curing catalyst. Examples of the curing catalyst include basic compounds such as metal hydroxides, metal alkoxides, metal carboxylates, metal acetylacetonates, hydroxides of onium salts, onium carboxylates, halides of onium salts, metal salts of active methylene compounds, onium salts of active methylene compounds, aminosilanes, amines, and phosphines, and Lewis acidic compounds such as organotin compounds, organozinc compounds, organotitanium compounds, and organozirconium compounds. As the onium salts, preferred are ammonium salts, phosphonium salts, and sulfonium salts.
Into the thermosetting composition of the invention, pigments such as an extender, a coloring pigment, and metallic pigments; additives for paint such as a UV absorber, a light stabilizer, a radical stabilizer, a yellowing-preventive agent which inhibits coloration at baking step, a coated surface regulator, a flowing regulator, a pigment dispersant, a defoaming agent, a thickening agent, and a film-forming auxiliary agent may be optionally incorporated, if necessary.
The thermosetting composition of the invention may be used as a clear or an enamel.